This application relates to preparation of thioalkyl aniline compounds which are useful as intermediates in the preparation of anthelmintic, antibacterial and fungicidal agents. Recently, a number of patents have described anthelmintics of the benzimidazole type. Examples are U.S. Pat. Nos. 3,956,499, 3,915,986, 3,905,991, 3,682,952, Dutch patent application No. 7,506,095, British Pat. No. 1,424,773, etc. Despite the disclosures of these patents, the present method for the preparation of such intermediates useful in such applications have not been heretofore disclosed.
In the prior art there are shown methods for preparing certain thioalkyl aniline compounds, such as the ortho-chlorophenyl thiocyanate, by reacting with n-propanol in the presence of sodium cyanide. However, a yield of only 29% was obtained. When the same reaction is repeated in dimethyl sulfoxide, the yield is increased to 50%; Tanaka, "Bulletin of the Chemical Society of Japan", Vol. 44, pages 2815-2820 (1971). The reaction of diaryl disulfides is also discussed by Tanaka in the same publication at Vol. 45, pages 536-539 (1972) in which the mechanism of the reaction is studied in some detail. Further elucidation of the mechanism of the initially described reaction between aryl thiocyanates, alcohol and cyanide is given by Tanaka in the same journal at Vol. 45, pages 834-836 (1972) in which thioiminocarbonates were produced in good yields. However, the production of thioalkyl anilines nevertheless could be improved by processes increasing the yields and allowing for recycle and reuse of expensive reagents. The present invention provides such improved process aspects.